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Fetal Femur Length from Gestational Age Chart (GAC) Comparison

Published: August 9, 2026Updated: August 16, 2026

This test measures the length of your baby’s femur bone using a reference chart based on gestational age to help assess fetal development.

Quick summary

["This helps monitor how your baby’s bones are growing during pregnancy."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
33167-8
Short code
Fet Femur Length from GA.Chitty94
Synonyms
Fet Femur Length from GA.Chitty94
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-estimated-from-chitty
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What This Test Measures

Your healthcare provider uses ultrasound imaging to measure the length of your baby’s femur bone. This measurement is compared against a standardized reference chart that accounts for gestational age (how far along you are in pregnancy). The chart helps determine if your baby’s bone development aligns with expected growth patterns.

Why It’s Done

This test is typically performed during prenatal ultrasounds to monitor fetal growth and development. It may be used to check for potential growth concerns, such as intrauterine growth restriction (IUGR), or to confirm normal progression of fetal development.

How It’s Performed

During an ultrasound, a transducer is placed on your abdomen to capture images of your baby’s bones. The provider measures the length of the femur using specialized software that correlates the measurement with gestational age.

What to Expect Before or After

There are no special preparations needed for this test. You may feel mild discomfort during the ultrasound, but it is generally quick and painless. Afterward, you can resume your normal activities.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Femur Length Assessment

Frequently asked questions

When might I hear about the results?
Results are usually reviewed immediately during the ultrasound and discussed with you by your healthcare provider. If additional follow-up is needed, they will share that information at your next appointment.
Is this test painful?
No, this test is not painful. You may feel some pressure or mild discomfort during the ultrasound, but it is a quick and routine procedure.
Can I eat or drink before this test?
No special preparations are required. You can eat and drink normally before the ultrasound.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy